There's a huge economic literature on this question, and of course there are disagreements. One of the reasons women earn less than men is that they are more likely not only to work part time, but also, when they're working full time, to work fewer hours. It's related to the problem of the sexual division of labour, but I wouldn't call that wage discrimination.
What we find--and this is what the pay equity applications do--is that when you actually go down and evaluate the kinds of jobs women do--for example, secretarial work or certain kinds of manufacturing--on an objective set of factors, we're still finding gaps of the order of 10% to 15%, which is not the entire.... That's why I used the qualification “to a large extent”; I didn't say “entirely” due to wage discrimination.
The evidence from the economic studies is that there are still prejudices and historical distortions of the value of the service jobs that women do, and that they are still not paid for comparable worth.